Various electronic devices such as an air conditioner, a windshield wiper or a power window are mounted in a vehicle, such as a passenger car or a freight car. These electronic devices are electrically connected with an electronic control unit (ECU), which includes a computer or the like, and a wire harness. Power and control signals are transmitted between these electronic devices and the ECU via the wire harness. The wire harness is provided with a plurality of electric wires and connectors which accommodate the terminal metal fittings connected to the terminals of the electric wires.
Conventionally, the ECU is provided with input/output parts for every electronic device connected to the ECU. Since connection circuits (namely, electric wires) exclusive for every electronic device are needed, the circuit number of the wire harness (namely, the number of electric wires) which connects the ECU and the electronic devices increases as the number of the electronic devices controlled by the ECU increases. Therefore, there are problems that the cost of the wire harness increases, the wire harness is hardly routed and the weight of the wire harness increases. Further, besides electronic devices that are normally mounted in a vehicle (namely, electronic devices indispensably mounted in a vehicle, hereinafter referred to as “standard electronic devices”), there are electronic devices that are mounted as optional equipments (that is, electronic devices optionally mounted in the vehicle, hereinafter referred to as “optional electronic devices”) in the vehicle. For every combination of electronic devices mounted in a vehicle, a wire harness provided with different circuits needs to be prepared, and there are problems that the types of wire harnesses increase and the cost increases.
A technique which solves these problems is proposed by the present applicant in Patent Literature 1. A wire harness, which is included in an electronic device control system shown in Patent Literature 1, is provided with a relay connector unit which relays the communication of the plurality of electronic devices and the ECU and is provided with a communication control function. The relay connector unit is provided with a plurality of circuits (terminals) to which the electronic devices are connected. By referring to circuit identification data contained in information received from the ECU, the relay connector unit transmits the information to the electronic device connected to the circuit which the circuit identification data indicates. The relay connector unit adds to information received from an electronic device the circuit identification data which indicates the circuit to which the electronic device is connected, and transmits to the ECU.
Thus, since the relay connector unit which has a communication control function is provided in the wire harness, and the ECU and the plurality of electronic devices are connected via the relay connector unit, the communication of the ECU and the plurality of electronic devices is multiplexed. Therefore, the ECU and the plurality of electronic devices can be connected by using a common circuit, and the circuit number of the wire harness can be reduced. When the combination of the mounted electronic devices (that is, the combination of optional electronic devices) is changed, it is possible to only change the connection circuit of the wire harness which is connected between the optional electronic devices and the relay connector unit. Therefore, even when the combination of optional electronic devices is changed, the circuit of the wire harness which is connected between the ECU and the relay connector unit can be commonly used without being changed. In this way, the problems which are mentioned above, such as the cost increase of the wire harness, the difficulty in arranging the wire harness and the increase of the weight of the wire harness, can be solved.